1. Field of the Invention
The present invention relates to an optical recording and/or reproducing apparatus, and more particularly, to an optical pickup actuator having a structure that significantly reduces and can prevent the transfer of heat generated from a coil of a driving unit to a lens, and an optical recording and/or reproducing apparatus employing the same.
2. Description of the Related Art
In general, optical recording and/or reproducing apparatuses, such as compact disk players (CDPs) or digital versatile disk players (DVDPs), include optical pickups to record and reproduce information with respect to an optical disc that is a recording medium. The optical pickup is accommodated on a turntable and records information by emitting light to the optical disc through an objective lens or reproduces information by receiving the light reflected by the optical disc, while moving in a radial direction of the optical disc that is rotated by a spindle motor. The optical pickup includes an optical pickup actuator that drives the objective lens in a track direction and a focus direction of the optical disc so that a light spot is formed at a desired position on a track of the optical disc.
Since portable apparatuses such as notebook computers are made thin and light, the optical pickup actuator that is installed in the optical pickup of the portable apparatuses must be slim. Thus, a reflection mirror to guide light towards the objective lens is adopted in the optical pickup. In order to reduce the distance between the objective lens of the optical pickup and the reflection mirror, so as to meet the need of being slim, an asymmetrical optical pickup actuator has been suggested in which a drive axis of the optical pickup actuator and an optical axis of the objective lens are differently arranged.
FIG. 1 is a perspective view illustrating a conventional asymmetrical optical pickup actuator. FIG. 2 is a sectional view, taken along line A–A′ of FIG. 1, illustrating a portion where a bobbin and an objective lens are combined.
Referring to FIG. 1 and FIG. 2, the conventional optical pickup actuator includes a bobbin 12 where an objective lens 11 is installed, a plurality of suspension wires 15 enabling the bobbin 12 to suspend with respect to a holder 14 that is installed on a base 13, and a driving unit to drive the bobbin 12 in a focus direction F and a tracking direction T.
The driving unit includes a focus coil 16 and a tracking coil 17 installed at the bobbin 12 and a pair of a magnet 18 and a yoke 19 which generate an electromagnetic force to drive the bobbin 12 by interacting with the current flowing in the focus coil 16 and the tracking coil 17. The focus coil 16 and the tracking coil 17 are capable of moving together with the bobbin 12 while the magnet 18 and the yoke 19 are fixedly installed on the base 13.
PCBs 20 to apply current to the focus coil 16 and the tracking coil 17 are arranged at both sides of the bobbin 12. A bond 21 is coated on a surface of the bobbin 12 in order to prevent the optical disc from being damaged due to collision between the bobbin 12 and the optical disc.
In the above structure, current is applied to the focus coil 16 and the tracking coil 17 via an electromagnetic force. The electromagnetic force is generated from the interaction of the current flowing through the focus coil 16 and the tracking coil 17 and the magnetic field formed by the magnet 18. The bobbin 12 moves in the focus direction F and the tracking direction T by the electromagnetic force. Accordingly, the objective lens 11 mounted on the bobbin 12 moves in the focus direction F and the tracking direction T.
However, in the conventional asymmetrical optical pickup actuator, since the coils 16 and 17 directly contact the bobbin 12 where the object lens 11 is mounted, a heat transfer problem may easily occur as a result of heat being generated when current is applied to the coils 16 and 17 for driving. That is, the heat generated from the coils 16 and 17 is transferred to the bobbin 12. The heat is easily transferred to the objective lens 11 directly contacting the bobbin 12, thereby deforming or damaging the objective lens 11. In particular, since the objective lens 11 is generally made from plastic material by an injection process, the objective lens 11 can easily deform due to inferior thermal-resistance properties. As a result, serious errors may occur in the operation of the optical recording and/or reproducing apparatus.
Furthermore, in a slim optical recording and/or reproducing apparatus, since the optical pickup actuator is installed in the optical pickup and the size thereof is smaller than the apparatuses of different types, the dissipation of heat is relatively difficult and the problem due to heat becomes more serious.
Many types of optical discs are produced, among which there are many low quality discs that exhibit a large amount of deformation and vibration during rotation. Accordingly, the optical disc and the optical pickup actuator frequently collide with each other. In such cases, the surface of the optical disc is damaged and, when the damage is severe, the recording and reproduction of information with respect to the optical disc is not possible.
To prevent this problem using conventional technology, a bond 21 with flexibility and buffering features is coated directly on the surface of the bobbin 12 so that the damage of the optical disc due to collision against the bobbin 12. However, it is inconvenient to coat the bond 21 directly on the surface of the bobbin 12.